PHP with GD + TTF fonts problem

Hi,

I have compiled the 'gd.so' module successfully using the osx.topicdesk.com tutorial, except 2 changes. I had to edit /usr/X11/lib/libpng.la and change '26' to '24' as described here:
http://sarth.thallos.org/search/label/libtool

And I also had to add '--with-gd=shared' to the 'configure' line.

Basic GD functionality is now working fine with the standard Apple installed PHP 5.2.6, but if I run the following PHP script, I see the following repeated many times in the error_log:

The script:
--------------------------
$width = 100;
$height = 100;
$filePNG = 'image.png';
$font_size = '29';
$font = 'monofont.ttf';
$code = 'test';


//first box
$im = ImageCreateTrueColor($width, $height);
$red = ImageColorAllocate($im, 255, 0, 0);
ImageFillToBorder($im, 0, 0, $red, $red);
imagepng($im,$filePNG);
ImageDestroy($im);

$textbox = imagettfbbox($font_size, 0, $font, $code) or die('Error in imagettfbbox function');
--------------------------

error_log
--------------------------------------------------------
[Thu Aug 14 16:22:53 2008] [notice] Apache/2.2.8 (Unix) mod_ssl/2.2.8 OpenSSL/0.9.7l PHP/5.2.6 configured -- resuming normal operations
THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTIONALITY___YO U_MUST_EXEC_() to debug.
The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec().
Break on _THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTIONALITY___Y OU_MUST_EXEC_() to debug.
..
.
.. same thing repeats many times
--------------------------------------------------------

Any ideas on why this would happen? If I remove the last line (the imagettfbbox call), it works fine. It seems I am missing something to do with truetype or freetype? But phpinfo() says that everything is enabled and FreeType support is enabled, Freetype Linkage is "with freetype", and Freetype Version is 2.3.5.